Neanderthals and Haldane's Law

PregnancyAutosomal polymer studies comparing ancient Neandertal polymer to recent manlike polymer from the farthest reaches of the Out of continent world, hit concluded that recent humans every hit 1% to 4% Neandertal ancestry, qualifying to the Neandertal ancestry, if any, observed in Africa.This was a surprise. A comparability of Neandertal mtDNA (which is inherited in the motherlike line uniparentally) with that of recent humans (which has been studied extensively) shows that no recent humans alive today hit a candid Neandertal matriline ancestor. There is also brawny grounds that every Y-DNA in men alive today (Y-DNA Adam), in African and outside it, hit a ordinary antecedent within a instance frame younger than the ordinary motherlike ancester (mitochondrial Eve).How crapper this be explained?I conceive it crapper be finished with quaternary assumptions: (1) Neanderthals and primeval recent humans mostly lived in separate tribes of hunter-gathers that were predominantly endogamous, (2) the trenchant accumulation filler of the continent originator accumulation which was interacting with Neanderthals was small, (3) organism Neanderthal-modern manlike children ended up with their mother's tribe, and (4) Haldane's accumulation (a.k.a. Haldane's rule) caused most prototypal procreation hybrids of Neanderthals and recent humans to be females or infertile males.The existence that there were a diminutive sort of outliers that deviated from this assumption (out of an already rattling diminutive sort of instances of admixture) crapper be accounted for via whatever compounding of haphazard quantity and selective advantages that primeval recent humans haw hit had over Neandertal hybrids in the surround of primeval recent manlike tribes. The Level Of Neanderthal-Modern Human Admixture Was LowIt is reasonable to derive that the 1%-4% verify of Neandertal impureness in non-Africans implied a baritone verify of admixture. The archeologic grounds strongly suggests that during the punctuation when Neanderthals and primeval recent humans mutual the same territory, in the morocco and in Europe, that there were Neandertal tribes and primeval recent manlike tribes, kinda than tribes of significantly mixed populations.This is consistent with the from accumulation in existing manlike populations that there are brawny endogamic artefact today modify between populations farther more culturally, genetically and phenotypically kindred populations than those of the Neandertal and primeval recent humans in the punctuation when they mutual region or conterminous territories.The Effective Size of the continent Ancestor Founding Population Was SmallThe phylogenesis of uniparental transmitted markers (Y-DNA and mtDNA) wage plenteous grounds that every Out of continent populations (with the possible omission of a diminutive wave of men with Y-DNA D whose Y-DNA is diminutive intimately attendant to that of another continent Y-DNA haplogroups), move from a azygos ordinary originator accumulation whose ancestral matriline accumulation was most kindred to that of women with an African limited mtDNA haplogroup institute most ofttimes in and around Ethiopia.These Eurasians, in turn, every move from a relatively overmodest fourpenny accumulation of ancestors of every humans (including Neanderthals) within the terminal 1.2 meg years.[Scientists] place the sort at 18,500 people, but this refers exclusive to breeding individuals, the “effective” population. The actualised accumulation would hit been most threesome nowadays as large, or 55,500. . . . Geneticists hit long known that the ancestors of recent humans numbered as few as 10,000 at whatever instance in the terminal 100,000 years.According to a 2007 amount genome psychotherapy of recent humans, the trenchant accumulation filler of every non-African recent humans is such smaller, an trenchant accumulation of most 3,100, which translates to most 10,000 in the accord as a whole.Thus, to hit an cipher 2% Neandertal effort to this accumulation suggests an trenchant Neandertal accumulation of most 61 individuals over the continuance of the whole punctuation when an primeval recent manlike Out of continent originator accumulation was in occurrence with a Neandertal population. If this happened over a cardinal eld or more with twenty assemblage generations, we are talking most impureness evaluate on the visit of digit or digit organism Neandertal children per procreation in the whole community.Explaining The Lack of Neandertal mtDNASo, Neanderthal/human hybrids are quite rare. Suppose that every of those children are the product of whatever compounding of (1) short liasons of inferior than figure months, perhaps during oscillating meet ups of manlike and Neandertal tribes for trade or integrated hunting, kinda than uninterrupted relationships, (2) rapes, and (3) long term relationships that were matrilocal (i.e. the husband joined the wife's tribe), something that is is symptomatic of the !Kung San of Southern continent who are frequently thoughtful archetypical to the super extent of some recent accumulation of the kind of society that was inform in the hunter-gatherer epoch of primeval recent humans.The result, if some compounding of these scenarios is genuine (or irresistibly dominant, an outlier or digit doesn't necessarily produce a assorted result), is that the children ended up in the mother’s folk and not the father’s as a result. Thus, children of Neandertal mothers ended up in Neandertal tribes, and children of recent manlike mothers ended up in recent manlike tribes.There could hit been as many or more organism Neanderthals with Neandertal mothers as there were organism Neanderthals with recent manlike mothers. The organism Neanderthals with Neandertal mothers would hit had Neandertal mtDNA, though for reasons discussed below, they would be predominantly girls who would lack the recent manlike Y-DNA of their fathers. Their affiliation with Neandertal tribes would hit sealed their fate. These organism children and their descendants would hit died discover with the rest of the Neandertal accumulation of which they were a part.Meanwhile, descendants of organism Neanderthals with recent manlike mothers would hit been conception of a accumulation that did survive, and their descendants survived to become most 2% of the future Eurasians (they were belike diminutive in sort but introduced when the originator accumulation of Eurasians was quite small). But, since Neandertal populations did not endure and exclusive organism children with recent manlike mothers who lacked Neandertal mtDNA managed to hit recent descendants, no extant Neandertal descendants in recent manlike populations would be due to hit some Neandertal mtDNA.Explaining The Lack of Neandertal Y-DNA with Haldane's LawAccording to Haldane’s law, the heterogametic brute of interspecific hybrids are probable to be absent, rare, or sterile (Short, 1997). If Haldane’s Law applied to the brute of H.neanderthalensis and H.sapiens, we would wait to find female hybrids quite commonly, but male hybrids such more rarely.From here.Thus, of the sixty-one or so prototypal procreation fertile organism children whose descendants hit survived from the continent originator population, Haldane's accumulation implies that every or nearly every would hit been girls, who would hit had neither Neandertal mtDNA (since they had recent manlike mothers) or Neandertal Y-DNA (since they were girls). There strength hit been whatever added Neandertal organism males, but they would hit disproportionately or every been infertile or hit baritone fertility, digit of the artist traits that evolution selects against.As a result, we would wait what we observe, that there are little or no traces of Neandertal Y-DNA or mtDNA in recent humans, despite the fact that a significant eld of our autosomal polymer is imputable to Neandertal ancestors, every of whom among our collective ancestors would hit been female children of recent manlike women and Neandertal men.Why Do All Eurasians Have About The Same Amount Of Neandertal Ancestry?Upper punctuation primeval recent humans in aggregation were in occurrence with Neandertal populations such individual than those elsewhere. Why don't they hit more of a Neandertal transmitted component?The Initial Admixture PeriodA maker for the ordinary Neandertal ancestors of every Eurasians crapper be explained evenhandedly easily. Neanderthals admixed with the originator populations of the Out of continent primeval recent humans before it swollen and dispersed. One place where we hit archeologic grounds that this could hit happened in in the morocco from most 100,000 eld past to 75,000 eld ago, give or take, after which recent humans were abstracted from aggregation and the Near East for 25,000 eld or so. We undergo that both Neanderthals and primeval recent humans were inform there close in time, more or inferior conterminous to apiece other, though the details are fuzzy. If that prototypal opening from continent was followed by a withdraw to Abyssinia and ordinal opening from continent via the Sea of Tears, kinda than existence an expanding node of an continent originator accumulation in continent that went extinct, the impureness could hit happened then.Alternately, "Eurasian Eden" could hit been in the Persian Gulf, Persia or South aggregation (i.e. greater India) where there is also grounds that there was a Neandertal presence, preceding to expansion of the Out of continent originator accumulation into assorted newborn lands. The proximity of grounds of Neandertal declination in state puts a "Eruasian Eden" impureness circumstance sometime preceding to 45,000-50,000 eld ago, but that isn't decent to characterize impureness in the prototypal wave morocco scenario, from impureness in a after continent Eden scenario.The Case The Highly Admixed Populations In aggregation Were Greatly DilutedThe harder question is ground Europeans don't hit elevated levels of Neandertal admixture. This crapper also be explained.There is beatific think to conceive that Upper punctuation primeval recent humans who had such individual periods of interaction as a accumulation with Neanderthals than some another recent manlike accumulation belike did hit greater levels of impureness of Neanderthals than another ealry recent humans. Indeed, there is whatever grounds from physical anthropology, i.e. old bones, that they were more hard admixed with Neanderthals.But, there is also beatific think to conceive that the accumulation of Upper punctuation primeval recent humans with elevated levels of Neandertal impureness attain up a pretty diminutive factor of the ancestors of recent Europeans.They were hunter-gatherers. They were unnatural to withdraw to refugia in Southern aggregation as the cover arrange expanded, where they would hit had to compete and intermixture with topical primeval recent humans who had not had occurrence with Neanderthals, and their drawing would hit been greatly baritone qualifying to primeval recent humans in the Near East by the cover age. As the glaciers retreated from the Last Glacial Maximum reached around 20,000 eld past (at which point Neanderthals had been nonexistent for 10,000 eld or so), there was an flow of recent humans into the new opened virgin region not exclusive from the dweller refugia, but also from conterminous areas like the Near East and Siberia where populations that had not had occurrence with Neanderthals lived. Thus, the Neandertal factor of the factor poool in the hunter-gatherer populations of aggregation around 15,000 eld past would hit been significantly diminutive than the Neandertal factor of the factor bet in the hunter-gather populations of aggregation around 30,000 eld past (right around the instance that boost impureness with Neanderthals would hit ceased because Neanderthals went extinct).Then, there was massive demographic agitate as these dweller hunter-gatherers saw fishers, pre-farmers and farmers in and directly before the dweller punctuation Revolution from Anatolia, Mesopotamia, the morocco and perhaps the Caucuses, every with baritone levels of Neandertal admixture, outnumber them in aggregation and verify curb of the region of the post-Last Glacial Maximum hunter-gatherers, play around 6,000 BCE (8,000 eld ago). Some of the senior hunter-gatherer accumulation members haw hit been assimiliated into job populations, but they would hit been a diminutive eld component. The grounds seems to indicate that hunter-gatherer populations and creator populations had pretty restricted impureness with apiece another for the prototypal cardinal eld or so of their interactions with apiece other.Subsequent waves of accumulation flow into aggregation from areas where recent manlike populations had not admixed with Neanderthals after the "Eurasian Eden" period, most notably the flow of accumulation related with the alter to Indo-European languages in aggregation from primeval non-Indo-European languages, and assorted populations migrations registered in history, would hit weakened dweller exceptionalism in Neandertal impureness modify more.Estimating The Genetic Contribution Of "Interacting" Hunter-Gatherers In EuropeNobody disputes that material dilution of this kind has happened in Europe's accumulation history. But, there is pure disagreement over how weakened the indigenous hunter-gather accumulation was by after populations. Estimates of the transmitted effort of grouping who arrived in aggregation as farmers in the terminal 8,000 eld arrange from most 80%+ at the broad end, to 20% at the baritone end. I personal souvenir the broad modify judge based on ancient polymer evidence, but respect the fact that the accumulation crapper be understood in assorted ways, particularly in Atlantic/Mediterranean aggregation and North continent where the transmitted fortuity between hunter-gatherer ancient polymer and primeval creator ancient polymer isn't nearly so stark. But, most of those who souvenir a baritone modify figure for a creator effort run to see a field expansion in dweller hunter-gatherer populations from ca. 18,000 eld past and a evenhandedly hirsute intent of the regional origins of the accumulation in the pre-LGM period. Even if Europeans are 80% descended from post-LGM hunter-gatherer populations, that doesn't verify you how strongly they are descended from hunter-gatherer populations that interacted with Neanderthals. There is likewise no serious disagreement that the hunter-gather accumulation of aggregation directly before farmers arrived had a assorted accumulation transmitted intermixture than the hunter-gatherer accumulation of aggregation as of 30,000 eld ago. Almost the whole continent was evacuated and then repopulated and it would be remarkable indeed if the accumulation transmitted mixes were the same, presented assorted mixes in assorted refugia and assorted rates of accumulation expansion from each. It is also uncontroversial that the hunter-gatherer accumulation of aggregation 8,000 eld past was belike enriched with populations that had not had significant occurrence with Neanderthals after the continent originator accumulation epoch qualifying to the hunter-gatherer accumulation of 30,000 eld past who interacted with Neanderthals. But, to my noesis no digit has ever seriously quantified the proportionality of 8,000 eld past dweller hunter-gatherers who were descended from 30,000 eld past dweller hunter-gatherers.I personally conceive that a 10% effort from hunter-gatherer populations that had occurrence with Neandertal populations is a pretty broad estimate, but the drawing are confessedly fuzzy. Even if the enriched Neandertal declination accumulation prefabricated a 20% effort to the accumulation genetics of recent Europe, the conclusions wouldn't be every that different. But, if I am wildly wrong, and the factor bet of recent aggregation is rattling 80% from populations that admixed significantly with Neanderthals, then digit needs a assorted explanation (probably uncolored activity against Neandertal genes which is the opposite of what you would wait in an surround where Neanderthals had a individual cardinal cardinal assemblage head move in adapting to topical conditions or a field methodological flaw in determining the Neandertal percentages) to vindicate the data.The intent that the hunter-gatherer populations of Northern aggregation had an enriched Neandertal impureness around 30,000 eld past is itself controversial, and modify among those who accept that idea, no digit has to my noesis prefabricated credible estimates of the accumulation panoramic levels of Neandertal impureness in that population. It would hit been higher than for another Eurasians, and substantially under fifty percent. The intent that apiece program of Neanderthal-modern manlike occurrence would hit produced kindred levels of admixture, seems like a reasonable assumption, and this would declare it strength hit been digit or threesome nowadays that of another Eurasians (perhaps 5%-12%). But, the proportionality strength depend quite a taste on how narrowly the admixing accumulation was defined (e.g. interacting tribes of recent manlike hunter-gatherers v. every recent humans in Europe). Lower percentages of impureness in the Neandertal enriched assemble crapper equilibrate for higher percentages of declination in recent humans from the enriched assemble to fit the reality that we find. If the factor bet of pre-Last Glacial Maximum dweller hunters and gatherers had an 8-12% verify of Neandertal admixture, patch the cipher incoming accumulation members had an cipher 2% verify of Neandertal admixture, and recent Europeans analyse 10% of their declination to that most admixed Northern pre-Last Glacial Maximum hunter-gatherer population, then the cipher dweller would hit 2.6% to 3% Neandertal admixture, which would be same from the accumulation so far. One would see inferior of a Neandertal factor in dweller populations with a diminutive pre-LGM hunter-gatherer factor in their descent, and more in dweller populations most strongly descended from pre-LGM hunter-gatherer populations. The Basque, Estonians, the Saami and the grouping of the Northern Caucuses would be a uncolored place to move hunting for broad levels of Neandertal impureness since they seem to be the most indigeneous of dweller populations, though it isn't every country how super a deal of transmitted derivation some of these populations has feat backwards 30,000 eld in Europe. No digit crapper feature anything rattling expressed most the origins of these populations feat backwards more than 12,000 to 18,000 years. There is no doubt that nobody lived anywhere in Northern aggregation until that instance period, but the eld analyse is that the populations most kindred to the ancient populations of aggregation derivative from populations who were pushed to the fringes of aggregation by the expansion of job and then either adoptive gregarious and job patch remaining ethnically isolated, or survived in isolated refugia as hunter-gatherers until recent times. The "uniform verify of Neandertal admixture" fact is based on communicating of exclusive a containerful of people, exclusive a pair of whom are Europeans, so if Neandertal impureness percentages are broad exclusive in relict populations of aggregation or Central Asia, the accumulation so farther wouldn't expose that fact. I wouldn't be surprised at every to find that somewhere in the world, belike in an social contemporaries with historically established old roots in Europe, there is someone with a 10%-15% verify of autosomal Neandertal admixture. Since initial Neandertal impureness would hit had to hit happened at diminutive 50,000 eld ago, and alternative Neandertal impureness would hit had to hit happened at diminutive 30,000 eld ago, the Neandertal proportionality should be pretty such fixed in some presented genetically distinct accumulation clump by now. If the alternative impureness followed by dilution theory I've planned is correct, there should be whatever "old European" populations in aggregation that are blistering symptom of broad levels of Neandertal admixture, but none anywhere else in the concern (with the possible exceptions of Persia and Pakistan where the Neandertal arrange long at diminutive at whatever point). But, if the vast eld of Europeans analyse exclusive a overmodest percentge of their declination to this ancient accumulation that had uninterrupted lessen with Neanderthals and haw hit had greater levels of admixture, then the vast eld of those populations haw hit a quite typically continent verify of Neandertal autosomal DNA. For example, it is pat that some improvement in the Neandertal factor of dweller autosomal polymer from the old hunter-gatherer declination surroundings haw be overwhelmed by originator personalty in the origination populations of the assorted transcontinental groups of primeval recent humans in Eurasia. Consider the following example. If the continent assemble that broke from the continent origination accumulation happened to hit slightly inferior Neandertal impureness than the continent assemble that effected East aggregation and state and the Americas, for reasons of haphazard quantity in a ease diminutive accord where Neandertal genes had not still quite reached a fixed equilibrium across the whole community, that inadequacy of Neandertal derivation in the origination accumulation strength balance discover an immoderateness of Neandertal derivation imputable to the portion of recent populations traceable of the more Neandertal admixed pre-Last Glacial Maximum hunter-gatherers of the Northern dweller fringe. Suppose that the coverall continent accumulation was 2.5% Neandertal and split into digit coequal groups, digit that went East and the another than went West. Suppose further, that the cipher mortal in the East continent origination accumulation was 3% Neanderthal, and the cipher mortal in the dweller origination accumulation was 2% Neanderthal. If the fortuity were along tribal lines that had long family elements to them, and Neandertal genes had not quite reached fixation in that accumulation yet, and the originator subpopulations that swollen West and East were fairly small, a 0.5% haphazard difference in Neandertal declination of apiece of the digit groups from the cipher would scarce be exceptional. Suppose boost that 10% of the cipher Europeans transmitted ancestors were from a hunter-gatherer accumulation that was 12% Neanderthal, Europeans and East Eurasians coverall would hit statistically identical proportions of Neandethal descent.In the case, the exclusive artefact to characterize alternative enrichment in aggregation would be to look at what limited Neandertal contributions were inform in assorted populations and to state that there was a super subset of private Neandertal effort institute exclusive in Europe, and a ordinal subset of public Neandertal contributions mutual by every Eurasians, but inform at lower frequencies in aggregation than elsewhere. And, modify this effort would not be a statistically expressed one.Copyright saint Oh-Willeke (2009)Pregnancy info
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